The ability to localize, recognize, isolate and interpret voiced sounds of another person are some of the most relied upon functions performed by the human auditory system. However, spoken communication often occurs in adverse acoustic environments including ambient noise, acoustic interference, and competing voices. Acoustic environments that include multiple speakers are particularly challenging because voices generally each have similar average characteristics and arrive from various angles. Nevertheless, acoustic isolation and localization of a target voice source are hearing tasks that unimpaired-hearing listeners are able to accomplish effectively, even in highly adverse acoustic environments. On the other hand, hearing-impaired listeners have more difficulty localizing, recognizing, isolating and interpreting a target voice even in favorable acoustic environments.
Previously available hearing aids typically utilize methods that improve sound quality in terms of simple amplification and listening comfort. However, such methods do not substantially improve speech intelligibility or aid a user's ability to identify the direction of a target voice source. One reason for this is that it is particularly difficult using previously known signal processing methods to adequately reproduce in real time the acoustic isolation and localization functions performed by the unimpaired human auditory system. Additionally, previously available methods that are used to improve listening comfort actually degrade speech intelligibility and directional auditory cues by removing audible information.
The problems stemming from inadequate acoustic isolation and localization signal processing methods are also experienced in machine listening applications utilized by mobile and non-mobile devices. For example, with respect to smartphones, wearable devices and on-board vehicle navigation systems, the performance of voice encoders used for telephony and systems using speech recognition and voice commands typically suffer in acoustic environments that are even slightly adverse.